In the examples of base transceiver stations with intelligent antennas according to the known art, a similar discrimination of the useful from the interferents is only partially made. This does not happen for a newly conceived base transceiver station, implemented by the same applicant, whose main innovative aspects have been protected by the following relevant patent applications:    EP 0 878 974 under the title “Communication Method for cellular telephone systems”, filed on May 16, 1997;    WO 99/33141 under the title “Discrimination process of a useful signal by a plurality of isofrequential interferent signals received by array antennas of base transceiver stations for cellular telecommunication and relevant method”.
In particular, the last mentioned application solves the problem of discrimination of the useful signal from a plurality of isofrequential interferents through a spatial filtering method, or beamforming, made on signals transduced by the array, previously submitted to a processing determining the number and the arrival directions of the waves incising on the array, distinguishing the useful from the relevant interferents.
Therefore, it is evident that in testing systems of base transceiver stations equipped with intelligent antenna, of old conception, the problem to simulate a radiofrequency scenario reflecting as precisely as possible what actually occurs in the reality, is not particularly perceived. This is a consequence of the fact that the beamforming algorithms there used do not discriminate (or do it in a rough and predictable manner) the useful signals from the relevant interferent echoes. It is then possible, and in the practice it generally occurs in the context of the known art, to use the old test equipment for receiver apparatus of the base transceiver stations, with omnidirectional or trisectorial antennas, apart from the simulation of the arrival directions of useful and relevant interfering echoes. Consequently, the actual test of the behaviour of the receiver complete with intelligent array antenna requires opportune test transmitters located, ad hoc, on the territory.
U.S. Pat. No. 5,539,772 is an example of a test equipment designed for verifies the performance of a digital satellite receiver belonging to a mobile terminal unit. As known, a geostationary satellite retransmits towards the mobile a phone call received from a satellite ground station, in turn connected to a public telephone network. The relevant claim 1 of the citation discloses an Apparatus for verifying performance of a RF receiver, comprising:                arbitrary waveform generator means for outputting an analog in-phase waveform and an analog quadrature waveform in accordance with sampled digital waveform data, said arbitrary waveform generator means including parallel first and second First-In-First-Out random access memories for storing the sampled digital waveform data;        the sampled digital waveform data comprising an in-phase waveform file stored in said First-In-First-Out memory and a quadrature waveform file stored in said second First-In-First-Out memory        each of the in-phase and quadrature waveform files including 60% root-cosine differential quadrature phase shift keyed data corresponding to successive frames of primary transmission channel data, co-channel interference data, adjacent channel interference data, and data relating to at least one of a plurality of impairments;        unity gain reconstruction filter means, connected to said arbitrary waveform generator means, for smoothing the analog in-phase and quadrature waveforms        vector signal generator means, responsive to the filtered analog in-phase and quadrature waveforms, for outputting a modulated RF signal; and        means for coupling an input of the RF receiver to the modulated RF signal output from said vector signal generator.        
A further independent claim of the same cited prior art is directed to a method for testing the receiver. In accordance with the claimed method a digital frame including a portion dedicated to reproduce the signal transmitted, via satellite, to a mobile telephone unit is generated. Except for the framed digital signal, the claimed method has the substantial features of the claimed apparatus. In the supporting description all the means involved in claim 1 generates a narrow band test signal, which because a mobile telephone unit activates only a telephone call at a time, contrarily to the base station which activates a plurality of simultaneous calls. Accordingly, the signal generated by the test apparatus of the citation is unsuitable to test a base station, where a suitable test signal should be of the multicarrier type. In the particular case of GSM with beamforming, a minimal realistic test apparatus is charged to synthesize a useful signal freely displaceable inside a wide radiofrequency band, i.e. the 880–915 MHz for extended GSM, plus one or more co-channel interferent having a presettable direction out of 360°. A more versatile apparatus could generate several sets of similar signals at the various frequencies. No suggestion is given in the citation about the design of such a test apparatus.